Field
The present disclosure generally relates to apparatus and methods for providing gases to a user. More particularly, certain aspects of the present disclosure relate to such apparatus used for providing pressure support to a sleeping user, such as in the treatment of obstructive sleep apnea.
Description of Related Art
A common method of treating obstructive sleep apnea (OSA) involves a pressure device that provides breathing gases, typically air, to a user (often referred to as the patient) while the user is asleep. The pressure device can be any of a number of units that fall into the broad classification of PAP (positive airway pressure devices) or CPAP (continuous PAP).
Within this broad classification, there are wide variations. For example, some units include a function to provide a different pressure during patient inspiration than during patient expiration (e.g., BiPAP), some units provide an auto-setting or autotitrating mode, where the supplied pressure varies through the period of use in response to detected events. In this context, detected events may include snoring, hypopneas, or obstructive breathing. Units also may respond to patient awakening and mask removal, for example, by reducing the delivered pressure. Other units deliver a predetermined set pressure, which may be delivered at the same pressure night after night, or may be varied night by night as adjusted by a physician, or as automatically adjusted by the unit. Many units include a ramp function that begins automatically or by patient selection. The ramp function causes the unit to commence at a low pressure, which is sometimes settable, and causes the unit gradually increase pressure toward a highest pressure, which may be the predetermined treatment pressure or an intermediate pressure.
The units typically provide controlled pressure delivery. For example, the units typically include a flow generator, a pressure sensor sensing the pressure being delivered to the user, and a feedback control controlling the output of the flow generator based on a sensor signal so that the sensed pressure is maintained close to a demand pressure. Alternatively, the flow generator can include a fan having a known pressure and flow response. The output of the flow generator can be controlled to deliver a desired pressure using feedback from a flow sensor in the circuit. Alternatively, the flow generator may include a fan that provides a substantially uniform pressure at a given rotation speed across a useful range of flow. Pressure then can be controlled by setting a substantially constant motor speed.
Even for a lower pressure, such as a pressure at the start of a ramp cycle, most of these units supply a minimum pressure of 3 cmH2O or more. This is more comfortable for the user than the full treatment pressure and is sufficient to provide a substantial flow of breathing gases through the supply line to the user, which breathing gases exit through a bias flow port or a controlled leak port provided at or near the user interface (e.g., mask).